Manufacture of mellitic acid



O 17, 1939- B. JUETTNER MANUFACTURE OF MELLITIC ACID Filed April 5, 1937lNVENTOR Berna rd Jue-tfner MM; M

M5 ATTORNEYS Patented Oct. 11, 1939 2,176,348

UNITED STATES PATENT OFFICE MANUFACTURE OF MELLITIC ACID BernardJuettner, Pittsburgh, Pa., assignor to Carnegie Institute of Technology,Pittsburgh, Pa a corporation of Pennsylvania Application April 5, 1937,Serial No. 135,061

14 Claims. (Cl. 260-515) My invention relates to a process for theproterial may be treated to produce mellitic acid of duction of melliticacid, and more especially to a a high quality and with a good yield. Ingeneral, process for manufacturing mellitic acid from carmy processconsists of refluxing a carbonaceous bonaceous material, and has for itsobject to promaterial with an excess of an oxidizing acid such vide asimple, eillcient and inexpensive method as fuming nitric acid, with orwithout the pres- 5 by which mellitic acid may be produced. The ence ofa catalyst such as vanadic acid. After term "carbonaceous material" isused herein to prolonged boiling, say, for a period of two weeks, meancoal, coke, charcoal, graphite, carbon the whole mixture is evaporatedto dryness and blacks, and pitch. the residue then oxidized by boilingfor a con- Various reagents have heretofore been used by siderableperiod of time, say one week, with an 10 other workers to oxidizecarbonaceous materials excess of an oxidizing salt, in an alkalinesolution to mellitic acid, such as alkaline permanganate, such asalkaline permanganate, and then filtersodium hypochlorite, fuming nitricacid with ing. A high yield of mellitic acid of excellent potassiumchlorate, concentrated sulphuric acid, quality may be recovered from thefiltrate.

concentrated nitric acid, sodium chlorate and With high temperaturecokes and especially 15 osmium tetroxide, anodic oxidation, fuminggraphite, the superiority of the nitric acidnitric acid with vanadiumcatalyst. The yields alkaline permanganate oxidation is best illusof thepure acid were extremely small and in trated. After boiling Achesongraphite (200 most cases only crude products were obtained. mesh) withfuming nitric acid and ammonium The best yields were reported by H.Meyer and vanadate for two weeks, no visible change had 20 coworkers whooxidized carbonaceous material taken place. The material had still theappearfrom various sources by refluxing with fuming ance of graphite.But on subsequent treatment nitric acid and 0.2% vanadic acid. The crudewith alkaline permanganate, the graphite was mellitic acid was convertedinto the ammonium oxidized to mellitic acid. Graphite not presalt andpurified through the copper salt. Their oxidized with nitric acid wasnot perceptibly yields are based on the crude ammonium salt. attacked byalkaline permanganate. I

The yield of the pure acid is not given, but from The new procedureusing fuming nitric acid experiments I have conducted following theirand ammonium vanadate was applied to 700 C.

procedure, I am forced to conclude that the yields and 1000 C. cokes.Here the nitric acid oxidation were small. I have also found that theirproproceeded much further than with graphite and cedure using onlyfuming nitric acid and vanaintermediate compounds were formed which, ondium catalyst even for a prodonged oxidation subsequent alkalinepermanganate oxidation, period of two weeks was wholly ineffective withyielded mellitic acid. In all cases, a complete high temperature cokesfrom various coals. The conversion of the carbon to CO2, mellitic acidand oxidati n st p d t t formation of high acids forming solubleammonium salts was 35 molecular intermediate compoundseffected. The 1000C. coke produced almost I amjaware also that attempts have been madeexclusively c0; and mellitic acid while the 700 0.

to 5 carbonaceous matPflaI by the use of coke produced CO2,me1liticacid, and acids formalkahne oxidation This ing soluble ammonium salts.In no case was cedure resulted mamly m oxalic acid being graphitic acid,nor any other intermediate oxida- 40 formed wtih very little melliticacid, when low tion product of larger molecular size than mellitlctemperature cokes were employed as the start acid, to d in the finalproduct.

ing material. When high temperature cokes were employed as the startingmaterial, it was Yields of mew-tic acid M the treatment with found thatalkaline permanganate had extremely nitric acid and a catalyst followedby treat 45 little effect.

I have found that a very satisfactory yield of ment an oxidizingsalt'dper 100 gram mellitic acid may be obtained from carbonaceousmaterial material by first treating the material for a suitable periodof time with a suitable oxidizing Total acids Am i Mellitic acid acid,with or without the presence of a catalyst, ff 1113 331? gfggfig fifollowed by oxidation with an oxidizing salt such as alkalinepermanganate. Mellitic acid obtained by following my method is pure, ofexcel- 700 O.Edenborn c01 2 5% lent quality, and the yield is high. fggg f gygggg g- 55 The principal object of my invention is to graph te23.7 80.0 19.1

provide a process by which carbonaceou ma- The mellitic acid wasidentified by analysis and by preparing the neutral methyl ester.

In the practice of my invention, the apparatus illustrated in theaccompanying drawing may be employed. In the drawing:

Figure 1 is a diagrammatic side elevation of a vessel suitable for usein boiling certain mixtures; and

Figure 2 is a diagrammatic side elevation of a three-compartment cellsuitable for use in this process.

In Figure 1 of the drawing, there is shown an apparatus which can beconveniently used for boiling the mixture during a certain phase of theprocess. The apparatus consists of an iron vessel ill with a removablewater-cooled lid ii, through which lid a shaft i2 with a paddle adjacentthe bottom of the vessel passes. This stirring device is driven by asuitable prime mover, not shown. A tube i l passes through the cover H,and a cover i5 is fitted over the outer end of the tube. Through thistube materials may be introduced into the iron vessel from time to time.

Figure 2 represents a three-compartment cell comprising a vessel it ofnon-conducting material divided into three cells by porous membranes H,118, preferably made of parchment. In compartment A, a platinum anode i9is placed. This is called the anodic compartment. This compartment maybe provided with a cooling coil of non-conducting material such as glasswhich will not affect or be affected by the liquid in the anodiccompartment. In compartment C, a hollow cathode 20, formed from copperand having pipes 2i and 22 through which cooling water is circulated, isplaced. This compartment is known as the cathodic compartment. The anodeand the cathode are connected to a suitable source of direct currentelectricity. The compartment B is referred to as the middle compartment.This apparatus is more particularly described and claimed in thecopending application of Henry C. Howard, Ser. No. 135,038 filed April5, 1937. The following examples illustrate the invention.

Example I Coke was formed by heating Edenborn coal to approximately 1000C. One hundred grams of the coke (200 mesh), together with 1500 cc.fuming nitric acid (sp. gr. 1.5) to which 0.24 gram ammonium vanadatewas added, where refiuxed for 14 days in an ordinary Pyrex flask with arefiux condenser. Then the whole was evaporated to dryness in a steambath under a vacuum of approximately 20 mm. of mercury. The

, solid residue was dissolved in about 3 liters of water containing 200grams of potassium hydroxide and transferred to an iron vessel providedwith a double-walled, water-cooled lid with an efficient stirrer in thevessel (see Figure 1) The solution was brought to a boil and sufficientexcess potassium permanganate was introduced from time to time so thatthe color remained purple during the seven days of boiling. During thattime, less than 50 grams of potassium permanganate was used. The excesspotassium permanganate was destroyed with formic acid. The manganesedioxide was filtered ed and thoroughly washed. The filtrate wasconcentrated.-

and placed in the middle cell of a three-compartment cell with parchmentmembranes separating the three-compartment cell (see Figure 2). Theanodic and cathodic compartments were eavaasa filled with distilledwater. To obtain good conduction, about 50 cc. formic acid was added tothe alkaline filtrate. After electrolysis for four days with a currentnot exceeding 4 amp. at volts, the acids were found to have migrated tothe anode compartment. The cathodic .and

, anodic compartments were emptied and refilled with distilled watertwice during each 24 hours of the electrolysis. The combined anodicsolutions were evaporated to about 300 cc. and the mellitic acid wasprecipitated as the ammonium salt by adding the concentrated anodicsolution to 1500 cc. of a well cooled solution of ammonium hydroxide(sp. gr. 0.9). An insoluble precipitate was formed which was found to bepure ammonium mellitate free from oxalic acid or any other impurities.

The yield of the dried salt was 35. grams. Ai'ter drying for 48 hoursover sulphuric acid under a vacuum of about 20 mm. of mercury, the salthad the approximate composition or a hexahydrate. To obtain the freeacid, the ammonium mellitate was added to 1000 cc. of distilled watercontaining 50 grams of potassium hydroxide and 12 cc. formic acid. Themixture was electrolyzed as described above. The dried residue obtainedfrom the evaporated anodic solutions consisted of 22.5 grams ofanalytically pure mellitic acid.

Example II One hundred grams of triphenylene (9-10 benzophenanthrene)was added to 1 liters of nitric acid (sp. gr. 1.5) and refluxed for aperiod of two weeks. The whole was then evaporated to dryness over asteam bath under a vacuum of about 20 mm. of mercury. To the residue,200 grams of potassium hydroxide dissolved in 3 liters of water wasadded and the mixture boiled with constant stirring for one week in aniron vessel having a water-cooled lid and an agitator in the vessel (seeFigure 1). From time to time during the week, 800 grams of potassiumpermanganate was added at a rate such that the liquid always showed apurple color. The excess of potassium permanganate was destroyed byadding sodium formats (I-ICOONa). The MnO2 was filtered ofi and washed.The filtrate contained the mellitic acid as a potassium salt. Thefiltrate was then concentrated by evaporation at atmospheric pressureover a steam bath to a volume of about 1 liter. The filtrate was thenplaced in the middle compartment of a three-compartment cell with aparchment membrane separating the compartments (see Figure 2). To obtaingood conduction, about 50 cc. of formic acid was added to the alkalinefiltrate. The anodic and cathodic compartments were filled withdistilled water. Electrolysis was conducted for 4 days with a currentnot exceeding 4 amps. at 110 volts. The cathodic and anodic compartmentswere emptied and refilled with distilled water twice during each 24hours.

The combined anodic solutions obtained above were converted to melliticacid through the ammonium salt as described in Example I. yield was 67.2grams.

Example III Five hundred grams Clairton coke (-200 mesh) was refluxedfor a total period of 3 weeks with 5500 cc. nitric acid (sp. gr. 1.5)and 300 cc. nitric acid (sp. gr. 1.6). The nitric acid was added inportions. First 3000 cc. nitric acid (sp. gr. 1.5) was added. Afterboiling for a little more than a week, the volume of the nitric acid hadde- The creased very much, but the color of the mixture was still theinitial black. Then 300 cc. of nitric acid (sp. gr. 1.6) was added andboiling continued for 3 days more. The color still remained black.

.An attempt was made to filter off the insolubles.

This, however, did not work due to the colloidal nature of the reactionproducts. Therefore, the oxidation was continued by adding, first 2000cc. of nitric acid (sp. gr. 1.5) and later 500 cc. of nitric acid (sp.gr. 1.5). After about a week of further refluxing, the color had changedfrom black to light brown. It was allowed to cool and the insolubleswere separated by sedimentation and filtration. In this case filtrationwas not difiicult. The insolubles were then dried and further oxidizedwith alkaline potassium permanganate. Less than 100 grams of potassiumpermanganate were used during 6 days. The excess potassium permanganatewas destroyed with formic acid. The manganese dioxide was filtered offand washed. The filtrate contained the mellitic acid as a potassiumsalt. The filtrate was treated as was the filtrate in Example I. Theyield of mellitic acid was 71.4 grams.

Example IV One thousand grams of 200 mesh Fairmont coke was oxidizedwith 3 liters of nitric acid (sp. gr. 1.5) and 0.5 gram vanadic .acid ascatalyst at a temperature between (SO-70 C. for one week. The mixturewas then cooled and the insolubles were filtered off. The insolubleswere dried and then added to 15 liters. of water containing 500 grams ofpotassium hydroxide. The mixture was placed in an iron vessel providedwith a'doublewalled water-cooled lid and with a stirrer reaching intothe vessel, as described in the previous examples. After the solutionwas brought to boil, 11,000 grams of solid potassium permanganate wasadded within 3 days. After that time the color was discharged. Themanganese dioxide was filtered off and the mellitic acid recovered as inthe previous examples. The yield was 150 grams.

It is possible to recover the mellitic acid from the alkaline filtrateas obtained, for instance, in Example I, through the barium or calciumsalt.

' -The alkaline filtrate is made just slightly acidic,

for instance with hydrochloric or nitric or acetic acid, and treatedwith a soluble barium or calcium salt. The insoluble barium or calciummellitate is formed. This is filtered off and treated with a sufiicientamount of dilute sulphuric acid and the insoluble barium or calciumsulphates, separated by filtration, and the mellitic acid recovered byevaporation of the filtrate.

It is also possible to recover the mellitic acid from the alkalinefiltrate as the neutral methyl ester. The alkaline filtrate isevaporated to dryness and treated with an excess of dimethyl sulphate atroom temperature for several days. In this manner, the neutral methylester of mellitic acid is formed and the alkali hydroxide is changed toa sulphate. The inorganic matter from the coke, mainly silica, is alsopresent in this mixture. To obtain the ester, the whole mixture istreated with water and the excess dimethyl sulphate is decomposed byadding a bicarbonate. The insoluble material consisting of silica andester is filtered off and the ester is obtained by extraction withalcohol or acetone. The ester may be purified by recrystallization froma mixture of methyl alcohol and water.

Instead of using dimethyl sulphate for preparing the ester, a mixture ofmethyl alcohol and sulphuric acid may be employed. The well driedevaporation residue from the alkaline filtrate is suspended in adefinite volume of methyl alcohol and to this is added carefully abouthalf that volume of concentrated sulphuric acid containing coppersulphate as catalyst. After heating the mixture for one hour at 125 C.,it is poured into water when silica and ester separate. The ester isobtained by extraction as above.

In this method the inconvenient and lengthy operation of decomposing theexcess dimethyl sulphate is avoided.

The following table shows the yields in grams of mellitic acid per 100grams of the following matfiigials (pulverized to approximately 200 mesHeated at Pittsburgh coal".

Cellulose (cotton). Acheson graphite. Natural graphite. Activatedcharcoal Pitch from low-temperature tar 9-l0-bcnzophenantbrene Petroleumcoke The effect of heat treating the carbonaceous material beforesubjecting it to the process which I have invented is shown in the abovetable.

It may or may not be desirable to use a catalyst depending upon theconditions of the oxidation. If a large excess of nitric acid is used,the catalyst is of no advantage. If the amount of nitric acid is greatlyreduced, the catalyst may be of importance by speeding up the oxidationwith nitric acid. However, the yields of mellitic acid are the samewhether a catalyst is used or not. But the amount of permanganaterequired in the second stage may be reduced by using a catalyst in thefirst stage, if the nitric acid is not present in large excess. I havealso determined that the temperature to which the carbonaceous materialis subjected before treatment has an effect on the yield of melliticacid. For example, I have found that in general better results areobtained if the coke is formed at a temperature of not less than 700 C.I have also determined that if the time of treatment with nitric acid isincreased, the amount of potassium permanganate needed will bedecreased. The most economical process must be ascertainedexperimentally for each type of carbonaceous material. These data can bereadily obtained following the teachings of my invention.

It is evident that by the process which I have invented, mellitic acidcan be produced in any desirable quantities in an economical andexpeditious manner.

While I have specifically described the pre-- ferred embodiment of myinvention, it is to be understood that the invention may be otherwisepracticed within the scope of the following claims.

I claim:

1. In the process of making mellitic acid, the steps which consist oftreating a material selected from the group consisting of coal, coke,charcoal, graphite, carbon blacks, and pitch with nitric acid andvanadic acid followed by a treatment with an alkali metal permanganatein an alkaline solution.

2. In the process of making mellitic acid, the steps which consist oftreating a material selected from the group consisting of coal, coke,charcoal, graphite, carbon blacks, and pitch with nitric acid and acatalyzer followed by a treatment with an alkali metal, permanganate inan alkaline solution.

3. In the process of making mellitic-acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of heating the material, refluxingthe material with an excess of an oxidizing acid, evaporating themixture to dryness, dissolving the residue in an aqueous solution of ametallic hydroxide, boiling the solution with an excess of an alkalimetal permanganate, filtering the mixture, separating the acids, andrecovering the mellitic acid through the ammonium salt.

4. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of heating the material, refluxingthe material with an excess of an oxidizing acid, evaporating themixture to dryness, dissolving the residue in an aqueous solution ofpotassium hydroxide, boiling the solution with an excess of potassiumpermanganate, filtering the mixture, separating the acids, andrecovering the mellitic acid through the ammonium salt.

5. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of heating the material, refluxingthe material with an excess of an oxidizing acid, evaporating themixture to dryness, dissolving the residue in an aqueous solution of ametallic hydroxide, boiling the solution with an excess of an alkalimetal permanganate, filtering the mixture, and recovering the melliticacid through the barium salt.

6. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of heating the material, refluxingthe material with an excess of an oxidizing acid, evaporating themixture to dryness, dissolving the residue in an aqueous solution of ametallic hydroxide, boiling the solution with an excess of an alkalimetal permanganate in an alkaline medium, filtering the mixture, andrecovering the mellitic acid through the calcium salt.

7. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of heating the material, refluxingthe material with an excess of an oxidizing acid, evaporating themixture to dryness, dissolving the residue in an aqueous solution of ametallic hydroxide, boiling the solution with an excess of an alkalimetal permanganate, filtering the mixture, and recovering the melliticacid through neutral methyl ester.

8. In the process of making mellitic acid, the steps which consist oftreating a material selected from the group consisting of coal, coke,charcoal, graphite, carbon blacks, and pitch with nitric acid followedby a treatment with potassium permanganate in an alkaline solution ofpotassium hydroxide.

9. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps which consist of refluxing the material with anexcess of an oxidizing acid, evaporating the mixture to dryness,dissolving the residue in an aqueous solution of a metallic hydroxide,boiling the solution with an excess of an oxidizing salt in an alkalinemedium, destroying the excess of the oxidizing salt with an organicacid, filtering the mixture, concentrating the filtrate, placing thefiltrate in the middle compartment of a three-compartment cell, thecompartment being separated by a permeable neutral membrane, passing acurrent of electricity through the cell, collecting the anodic solutionand evaporating it to a reduced bulk, adding the reduced bulk to asolution of ammonium hydroxide, adding the precipitate to water,electrolyzing the mixture in a three-compartment cell as above anddrying the residue.

10. In the process of making mellitic acid by treating a materialselected from the group consisting of coal, coke, charcoal, graphite,carbon blacks and pitch, with an oxidizing acid, the step of treatingthe substance thus formed with a solution of an alkali metalpermanganate and an alkali metal hydroxide.

11. In the process of making mellitic acid by treating a materialselected from the group consisting of coal, coke, charcoal, graphite,carbon blacks, and pitch with fuming nitric acid, the step of treatingthe substance thus formed with an alkali metal permanganate in analkaline solution.

12. In the process of making mellitic acid by treating a materialselected from the group consisting of coal, coke, charcoal, graphite,carbon blacks, and pitch with nitric acid, the step of treating theinsoluble residue thus formed with a solution of an alkali metalhydroxide and an alkali metal permanganate.

13. In the process of making mellitic acid by treating a materialselected from the group consisting of coal, coke, charcoal, graphite,carbon black, and pitch by an oxidizing acid, the steps of drying theresidue and then treating the residue with .a solution of an alkalimetal hydroxide and an alkali meal permanganate.

14. In the process of making mellitic acid from a material selected fromthe group consisting of coal, coke, charcoal, graphite, carbon blacks,and pitch, the steps comprising heating the material with nitric acid,filtering the insolubles, drying the insolubles and then treating theinsolubles with a solution of an alkali metal hydroxide and an alkalimetal permanganate.

BERNARD J UE'I'I'NER.

